It is known from GB-A-828,568 to sew filter bags for filter sections, one or more sides of the bag being provided with a zip fastener for closing the bag when it has been pulled over a filter section. Subsequently, outside the bag, either at the outer or inner periphery thereof, a means closing the corresponding bag end is attached. This means may be a nozzle means. This known construction thus requires mounting work after the bag has been applied onto the section.
In another known construction, employed by the applicant, the filter bag, after having been mounted onto the section, is shrunk with hot steam so that it tightly embraces the section. Thereafter, a nozzle, usually of acid-resisting material, is mounted on the section and a hole is cut in the filter cloth through the filtrate discharge opening or openings of the nozzle.
This method is expensive and laborious, as well as difficult to perform for untrained personnel when exchanging the filter bag, e.g., in a paper mill.